Lot

A standardized trade size. A standard lot is 100,000 units of the base currency.

Trades aren't placed in arbitrary amounts — they're sized in lots. A standard lot is 100,000 units, a mini lot is 10,000 (0.1 lot), and a micro lot is 1,000 (0.01 lot). Lot size directly determines how much money moves for every pip the price shifts — bigger lot, bigger swing in profit or loss per pip.